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Quarterly Monitonng Report,Apnl 2001 <br />' Canepa's Car Wash(Park Street) <br /> May 28,2001 <br /> Page 5 <br /> from MW-2, MW-5, and MW-6 Low concentrations of MTBE were detected in. the groundwater <br /> samples collected from MW-3 and MW-4 The second quarter 2001 laboratory analytical results <br />' generally indicate that the area of groundwater contamination most impacted by petroleum hydrocarbons <br /> IS in the northern portion of the site in the vicinity of monitor wells MW-2 and MW-5 <br />' 5.2.1 DISCUSSION OF BENZENE CONCENTRATIONS <br /> The concentration of benzene has decreased with time in monitor well MW-2 as the groundwater <br /> elevation has increased (Figure 6, Appendix A) Benzene concentrations in MW-5 have generally <br />' increased as the groundwater elevation has increased (Figure 8, Appendix A) It is important to note that <br /> both wells are drowned, with 16 to 22 feet of water above the well screen Therefore the first <br /> groundwater, with potential eater BTEX concentrations, is not being sampled - <br /> j <br /> 5.2.2 DISCUSSION OF MTBE CONCENTRATIONS <br /> Concentrations of MTBE in monitor well MW-6 have decreased slightly over time, with a recent <br /> increase in October 2000 and decrease in April 2001 (Figure 7, Appendix A) There has also been a <br /> reappearance of low concentrations of MTBE in monitoring wells MW-3 and MW-4 <br /> 5.2,3 DISCUSSION OF OTHER ANALYTE CONCENTRATIONS <br /> Concentrations of toluene, ethyl benzene, total xylenes, and TPH-G have decreased over time in monitor <br /> Ile well MW-2, but all have increased in monitor well MW-5 (Table A, Appendix B) In general, <br /> concentrations of analytes have decreased as the groundwater elevation has increased, except in MW-5, <br /> which has seen an increase in contamination It is important to note that since all of the monitoring wells <br /> are drowned, the shallowest water with the potentially highest contaminant concentrations is not being <br /> sampled Therefore, the actual concentrations of the plumes have not been measured and are not known <br /> According to Figures 4 and 5, the plumes probably extend beyond the site, therefore the current <br />' monitoring wells cannot measure the northern extent of the contaminant plumes <br /> I <br /> I � <br /> �, CONDOR <br />